Hey Rob,
I've been flying the Dynali HS2 amphibie for a couple of days now. I really like it, but the sound was kind of annoying. I switched it to the Robinson R-22 sounds. Now it's better. Put this line at the top of your sound.cfg file to change the sound to the R-22.
[FLTSIM]
alias=P:\Microsoft Flight Simulator X\SimObjects\Rotorcraft\Robinson_R22\sound
product_code=FSIM
The product_code=FSIM line was already there, just leave it in and add the "alias=" line like the example above, changing the "P:\" to the drive you're using.